1. Field of the Invention
The present invention relates to a sewing machine with thread take-up mechanism which takes up a thread being led to a sewing needle to apply tension to the thread forming the stitches.
2. Description of the Prior Art
A conventional take-up mechanism is shown in U.S. Pat. No. 3,884,165. This take-up mechanism has a take-up lever located at an upper position of a needle bar and pivotally moved by a gear, and is adapted to take up the thread being led to the needle by reciprocal movement of the take-up lever in the vertical direction. Thus, with this conventional mechanism, since the take-up lever is located upward of the needle bar and away therefrom and is adapted to move pivotally, the distance between the take-up lever and the needle eye is great and also the directions of movement of the take-up lever and the needle bar are different from each other. As a result, when the thread is taken up, the thread is stretched largely between the take-up lever and the needle eye when the thread is made of a certain material, so that insufficient and unstable tension is applied to the thread forming the stitches. In addition, the conventional mechanism suffered from the problem that the whole mechanism becomes so large.
Further, U.S. Pat. No. 4,546,712 shows a take-up mechanism with a complicated structure comprising a take-up lever provided with a plurality of thread guiding fingers, and a plurality of hook-shaped thread catching levers. With this device, one of a plurality of threads is selected to be used in the sewing. However, during the sewing, all the threads are vertically moved together with the thread guiding fingers while the threads are brought into sliding contact with the inner peripheral surfaces of the eyes of the thread guiding fingers. Therefore, this arrangement of the take-up mechanism adversely affect the threads.
Furthermore, U.S. Pat. No. 2,191,129 shows a sewing machine in which a guide eye is directly formed in the upper end of the needle bar. In this machine, said guide eye takes up the thread in cooperation with a tension device disposed between the needle bar and the bobbin. Therefore, with this arrangement of take up device, the timing and stroke of the vertical movement of the needle bar and those of the thread taking-up action by the guide eye accord with each other. Although this feature raises no problem when the sewing machine is of the single yarn chain stitch sewing machine type, as in the case of this U.S. Pat. No. 2,191,129, wherein the amount of thread taken up is small and also no accurate timing of the taking up action is required, it is disadvantageous when the machine is of another type such as a lock stitch sewing machine because, in such a case, no proper stitches can be formed.